package com.pashanhoo.Thread.pool;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.ArrayDeque;
import java.util.Deque;
import java.util.HashSet;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;

/**
 * @author 胡庆安
 * @version V2.0
 * @Package com.pashanhoo.Thread.pool
 * @date 2020/10/23 14:01
 * @Copyright © 2010-2020 爬山虎科技（扬州）股份有限公司
 */
public class ThreadPool {
    Logger log = LoggerFactory.getLogger(ThreadPool.class);
    // 任务队列
    private BlockingQueue<Runnable> taskQueue;
    // 线程集合
    private HashSet<Worker> workers = new HashSet<>();
    // 核心线程数
    private int coreSize;
    // 获取任务时的超时时间
    private long timeout;
    private TimeUnit timeUnit;

    // 执行任务
    public void execute(Runnable task) {
        // 当任务数没有超过 coreSize 时，直接交给 worker 对象执行
        // 如果任务数超过 coreSize 时，加入任务队列暂存
        synchronized (workers) {
            if (workers.size() < coreSize) {
                Worker worker = new Worker(task);
                log.debug("新增 worker{}, {}", worker, task);
                workers.add(worker);
                worker.start();
            } else {
                // taskQueue.put(task);
                // 1) 死等
                // 2) 带超时等待
                // 3) 让调用者放弃任务执行
                // 4) 让调用者抛出异常
                // 5) 让调用者自己执行任务
                taskQueue.offer(task,1000,TimeUnit.SECONDS);
            }
        }
    }

    public ThreadPool(int coreSize, long timeout, TimeUnit timeUnit, int queueCapcity) {
        this.coreSize = coreSize;
        this.timeout = timeout;
        this.timeUnit = timeUnit;
        this.taskQueue = new BlockingQueue<>(queueCapcity);
    }

    class Worker extends Thread {
        private Runnable task;

        public Worker(Runnable task) {
            this.task = task;
        }

        @Override
        public void run() {
            // 执行任务
            // 1) 当 task 不为空，执行任务
            // 2) 当 task 执行完毕，再接着从任务队列获取任务并执行
            // while(task != null || (task = taskQueue.take()) != null) {
            while (task != null || (task = taskQueue.poll(timeout, timeUnit)) != null) {
                try {
                    log.debug("正在执行...{}", task);
                    task.run();
                } catch (Exception e) {
                    e.printStackTrace();
                } finally {
                    task = null;
                }
            }
            synchronized (workers) {
                log.debug("worker 被移除{}", this);
                workers.remove(this);
            }
        }
    }

    class BlockingQueue<T> {
        // 1. 任务队列
        private Deque<T> queue = new ArrayDeque<>();
        // 2. 锁
        private ReentrantLock lock = new ReentrantLock();
        // 3. 生产者条件变量
        private Condition fullWaitSet = lock.newCondition();
        // 4. 消费者条件变量
        private Condition emptyWaitSet = lock.newCondition();
        // 5. 容量
        private int capcity;

        public BlockingQueue(int capcity) {
            this.capcity = capcity;
        }

        // 带超时阻塞获取
        public T poll(long timeout, TimeUnit unit) {
            lock.lock();
            try {
                // 将 timeout 统一转换为 纳秒
                long nanos = unit.toNanos(timeout);
                while (queue.isEmpty()) {
                    try {
                        // 返回值是剩余时间
                        if (nanos <= 0) {
                            return null;
                        }
                        nanos = emptyWaitSet.awaitNanos(nanos);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
                T t = queue.removeFirst();
                fullWaitSet.signal();
                return t;
            } finally {
                lock.unlock();
            }
        }

        // 带超时时间阻塞添加
        public boolean offer(T task, long timeout, TimeUnit timeUnit) {
            lock.lock();
            try {
                long nanos = timeUnit.toNanos(timeout);
                while (queue.size() == capcity) {
                    try {
                        if (nanos <= 0) {
                            return false;
                        }
                        log.debug("等待加入任务队列 {} ...", task);
                        nanos = fullWaitSet.awaitNanos(nanos);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
                log.debug("加入任务队列 {}", task);
                queue.addLast(task);
                emptyWaitSet.signal();
                return true;
            } finally {
                lock.unlock();
            }
        }

        public int size() {
            lock.lock();
            try {
                return queue.size();
            } finally {
                lock.unlock();
            }
        }


    }
}

